Way overdue update on my 45 based DHT headamp.
In breadboard state, was really quiet.
After I boxed it up, as shown in the pic I posted way back, I had 60 hz humming. It was pretty bad on my hd800's.
Spent a long time trying different things, because quiet a bit of the wiring changed when I moved into the chassis.
It turned out that what finally resolved the problem is that I had added a CLC filter on my ac in line. The filter and ac lines were under the output tx's. Should have been obvious in hindsight.
Removed the filter, ran AC directly from IEC jack to power tx, and noise is almost gone. There is still a real small amount of hum I can hear if no music is playing, but you have to listen for it.
I am using the low impedance output tap from my output tx's.
So in summary, I was able to make a one box dht amp using 45's and the Tubelabs SE pwb that is quiet enough (although I can't call it dead silent). Sounds really good (IMHO).
Randy